| Monotectic alloys have attracted attentions for their unique potential applications because of their excellent physical and chemical characters. But most of monotectic alloys have large differences in density and melting point between the two constitutions, and have a large immiscibility gap in the phase diagram, so it is hard to fabricate homogenous microstructure.In recent years, with the development of the superconducting technology, superconducting high magnetic fields have been applied to material processing from ferromagnetic to all kinds of materials included non-ferromagnetic. The processing has become a newly material fabrication method. Especially the magnetic field could compensate gravity and form reduced gravity conductions, so it could restrain the segregation induced by gravity effect. In this paper, the special character of high magnetic field is used to study its effect on the solidification process of Fe-Sn monotectic alloys.The influence of high magnetic field on the microstructure of Fe-Sn monotectic alloys have been researched under a 12T high magnetic field and 1200℃vacuum furnace. The microstructures evolution and magnetic properties of Fe-46%Sn (hypo-monotectic) and Fe-49%Sn (hyper-monotectic) alloy have been discussed under different processing conditions such as magnetic flux density, temperature/time conditions, cooling rates. Moreover, some theoretical analysis about the phenomenon has been proposed. The main research results are as followings:1. Fe-rich phases are partly aligned along the high magnetic field direction when there is a high magnetic field. However, they are mainly irregular distributed in the form of dendrite without a high magnetic field.2. Under different high magnetic field, there are some different Fe-rich phase morphology. For Fe-46%Sn alloy, it forms bamboo-like morphology, aligned along the direction of magnetic field. For Fe-49%Sn alloy, it forms strip-like morphology, aligned parallel to the magnetic field direction. The orientation degree of Fe-rich phase is more obvious with the increasing of magnetic flux density. 3. The XRD analysis indicates that the diffraction peak of a-Fe (110) face in the longitudinal section of high magnetic field has increased in Fe-49%Sn alloy. Theoretical analysis indicates that [001] axis which parallel to (110) face is the preferential growth direction of a-Fe, so that a-Fe will be firstly induced grow up along [001] axis under high magnetic field, which makes Fe-rich phase align along magnetic field. However, the influence of magnetic field on the diffraction peak of a-Fe (110) face is not obvious in Fe-46%Sn alloy.4. The slower the cooling rate is, the easier to make Fe-rich phase rotate and orient in the initial stage of nucleation/growth of Fe-Sn alloy, which will promote the alignment of Fe-rich phases.5. The alignment of Fe-rich phases which are induced by a high magnetic field has played a role on the magnetic properties of Fe-Sn alloy. For Fe-49%Sn alloy, the saturated magnetization intensity Ms and the residual magnetization intensity Mr increase with the increasing of magnetic flux density and holding times, and the decreasing of solidified cooling rate. The coercive force He increases with the increasing of magnetic flux density and holding times, and decreases with the decreasing of solidified cooling rates. For Fe-46%Sn alloy, the influence of magnetic field on its magnetic properties has some fluctuation and not as obvious as Fe-49%Sn alloy. |
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